Device for producing or reproducing sound



- May 29; 1923.

. 1,457,075 c. HULBERT Y DEVICE F OR PRODUCING OR REPRODUCING SOUND original Filed March 21', 1917 3710241 foq C.H.Hulb e1 f Patented May 29, 1923. UNITED STATES PATENT OFFICE.

CLINTON H. HULBERT,

OF CHICAGO, ILLINOIS.

DEVICE IOR PRODUCING OR REPRODUCING SOUND.

Application. filed March 21, 1917, SeriaI'No. 156,428. Renewed October 18, 1922.

To all whom it may concern Be it known that I, CLINTON"HORACE HULBERT, a citizen of the United States, residing at Chicago, county of Cook, and- This invention relates to devices for producing or reproducing sound,"and particularly to telephone receivers. With. the

' usual construction of receivers now gener-.

ally employed, not more than two magnetic pole pieces are used, and as a result, the thin diaphragm becomes easily saturated opposite the pole pieces, so 'that only a limited quantity of magnetic lines of force Q 'may pass through,tl1ereby limiting the amount of current which may be effectively utilized. 7 J

I have provided means whereby the effective magnetic area of the diaphragm may be increased with the result that an increased quantity of magnetic lines of force may pass from the pole pieces through the diaphragm causing greater reasonance and thereby increasing the tonal quality of the instrument. The device may be. used as a receiver or atransmitter, but it is particularly applicable as em loyed in annunciating horns, such as emp oyed in railway stations, public halls and the like.

- In carrying' out my invention, I preferabl arrangethe electro-magnets in mul-. tiples of two, in inwardly projecting circular groups about a common center, the opposite poles being disposed inalternating relation, whereby the magnetic attraction exerted upon the'diaphragm is equally disposed, about the axis of said. diaphragm. I also prefer to arrange the permanent magnets, to which the electro-magnets are attached, of such form that their outer .ends are of greater cross sectional area than the inner ends, so that there will be heavy lines of magnetic force to concentrate at the pole points. Theoretically, the greater the number of pole pieces, the greater the resonance of the diaphragm, but for practical purposes, I 'have found that fromsix to eight pole pieces efiiciently distribute the electromagnetid lines of force throughout the diaphragm,

For the purpose of' illustration, I have shown two practical forms of my invention, it being understood, of course-that changes .there being four pairs) Serial No. 595,463.

in form, proportion, and minor details of c'onstructionmay be resorted to, without departing from the spirit of the invention, orsacrificing any of its advantages.

In the drawings Figure 1 is a vertical longitudinal sectional view through a telephone receiver constructed in accordance with. my invention;

through the same, and

'l igure 3 is a vertical longitudinal sectional view through an annunciating receiver.

Referring now to the drawings by numerals of reference, '1 designates a casing having a removable cover 2 with a central opening 3 of usual construction, the' diaphragm 4 being interposed between the edge of the casing 1 and the cover 2 in the .usual manner. Within the casing 1 are a plurality of'permanent'magnets 5 radially disposed about a common center and clamped to the bottom of the casing l by a plate 6 and fastening devices 7. The outer ends of the preferably of permanent magnets 5 are than their inner ends, and said outer ends are provided with ofl'set portions to which. the poles of .the'electro-magnetic windings 10 are secured, preferably by fastening devices ll. It will be observed that the poles 9 of the magnetic windings 10 project inwardly and upwardly'toward a common center, the ends of said magnets being relatively Figure 2 1s a transverse sectional new greater cross sectional area close to the comparatively thin diaphragm 4,

Inasmuch as the pole pieces 9- are arranged in multiples of two (in-the present instance force will be fractionally distributed about the common center over, area in excess of thatusually employed for devices of this character so that stronger current may be employed and greater resonance obtained from the diaphragm, resulting in a rela tively loud tone.

.If desired, thetonal quality of the device may be varied through the medium of the contact bar 12 on the rotating shaft 13, whereby the bar 12 may out certain electro-magnets.

In Figure 3, I have shown a slightly modified form of 'device embodying the same generic principle especially adapted employed in railway stations and the like.

,thelatter device being the lines of magnetic be cut in or cut for annunciators, such as I have provided a device of the class described in which a relatively thin diaphragm may be adapted to receive magnetic lines of force of comparatively great intensity because multiple paths are projvided for the linesof force so the aggregate current is fractionally distributed through the diaphragm. p It is to be understood, of course, that in order to add rigidity to the structure heretofore described, the casings 'may be it Will be seen that. thereto consisting of six or more nearly filled with an embedding material such as wax' or the like, as 'is somewhat now in practice in devices vof similar character. I

In a device of the class described, pennanent magnets, electro-inagnets connected located all on one side of the diaphragm arran ed in pairs of like poles, the poles of said e ectro-. disposed in circular series,-

magnets being the north'and south poles being arranged in alternating relation and. a diaphragm cooperating with said poles.

The foregoing specification sighed" at Washin on, District of Columbia, this QOth day of arch, 1917.

CLINTON H. H LBERTQ 

